The invention relates generally to systems for manipulating video signals and more particularly to a digital system which manipulates moving video images.
Previous video special effects systems utilized analog circuitry for directly manipulating an analog video signal. These analog systems are difficult to maintain and operate, require complex and expansive analog circuitry of a critical nature and must be syncronized with the video input signal. These systems are generally quite limited as to the special effects they can perform and are not easily reprogrammed to perform other effects.
More recently special effect digital systems have been devised which utilize the concept of restructuring memory addresses upon read out to produce a few limited special effects. They are also able to convert between the NTSC North American system of television and the PAL European system. Finally, the most recent form of digital special effects systems disclosed in my pending application Ser. No. 436,066, now U.S. Pat. No. 4,533,952, entitled, "Digital Video Special Effects System," which uses an address restructuring technique to provide a simple and economical means for producing rotative, three dimensional, and other special effects. This system utilizes a coordinate generator, syncronized with the video input signal to produce address signals. The address signals are generated in a predetermined sequence and a predetermined number of such signals are produced during each of the scanned signal portions of the video input signal. A key video signal is modified by an analog to digital converter which produces digital samples of the key video signal syncronized with signals of the coordinate generator means. The address signals correspond to respective memory locations in a memory which stores the pixel information pertaining to the key video signal in the respective memory locations defined by the address signals produced by the coordinate generator. In this manner a key map is produced in the memory which directly corresponds to the video picture defined by the key video signal. Thus, each memory location contains the information necessary to define an on/off pixel that is, it corresponds to a dot having predetermined luminance in the video screen image. A microprocessor is then used with a hardware implemented manipulator to call out selective ones of the pixels to new coordinates of the output scan. The coordinate reassignments being selected in accordance with solutions to a predetermined generalized equation. Only the output address is recalculated. Pixel information of the key video signal remains in its original location in the memory. In this manner, the original key map is preserved and only the output sequence needs to be calculated by the microprocessor. This also improves data access feed since a high speed random access memory may be utilized. The video special effects is driven by software which may be in the form of programmable only memories which may be easily removed or selected from a plurality of available ones. The original pixel information is preserved in the memory but the information is presented on the video screen at coordinate positions which do not necessarily correspond with the position of the stored image. New coordinate positions locate the pixel information on the video screen in a location corresponding to a solution of an effect defining equation.
The system described in my previous application handles one pixel at a time and will not effectively handle moving video images. To handle moving video images, data in the video memory must be addressed more than one pixel at a time since each pixel is a function of several pixels around it. To ensure high visual quality, an interpolation scheme must be employed. The problem is solved by using a suitable memory organization and an addressing scheme by which to pull the appropriate pixels at the appropriate time.